Monitor Windows event log data

Windows generates log data during the course of its operation. The Windows Event Log service handles nearly all of this communication. It gathers log data published by installed applications, services and system processes and places them into event log channels. Programs such as Microsoft Event Viewer subscribe to these log channels to display events that have occurred on the system.

Splunk Enterprise can monitor event log channels and files stored on the local machine, and it can collect logs from remote machines. The event log monitor runs as an input processor within the splunkd service. It runs once for every event log input that you define in Splunk Enterprise. If you have Splunk Cloud and want to monitor event log channels, use the Splunk Universal Forwarder to collect the data and forward it to your Splunk Cloud deployment.

New for versions 6.4.5 and later of Splunk Enterprise, the Windows Event Log monitoring input has improved performance.

Why monitor event logs?

Windows event logs are the core metric of Windows machine operations - if there is a problem with your Windows system, the Event Log service has logged it. Splunk Enterprise indexing, searching, and reporting capabilities make your logs accessible.

Prerequisites to monitoring event logs

Activity:

Required permissions:

Monitor local event logs

Splunk Enterprise must run on WindowsSplunk Enterprise must run as the Local System user to read all local event logs

Monitor remote event logs

Either Splunk Enterprise or a universal forwarder must run on the Windows machine from which you want to collect event logs

Splunk Enterprise or a universal forwarder must run as a domain or remote user with read access to Windows Management Instrumentation (WMI) on the target machine
The user that Splunk Enterprise or the universal forwarder runs as must have read access to the event logs you want to collect

Security and remote access considerations

Splunk Enterprise collects event log data from remote machines using either WMI or a universal forwarder. Splunk best practice is to use a universal forwarder to send event log data from remote machines to an indexer. See The universal forwarder in the Universal Forwarder manual for information about how to install, configure and use the forwarder to collect event log data.

To install forwarders on your remote machines to collect event log data, you can install the forwarder as the Local System user on these machines. The Local System user has access to all data on the local machine, but not on remote machines.

To use WMI to get event log data from remote machines, you must ensure that your network and Splunk instances are properly configured. You cannot install the Splunk platform as the Local System user, and the user you install with determines the event logs Splunk software sees. See Security and remote access considerations in Monitor WMI-based data for additional information on the requirements you must satisfy to collect remote data properly using WMI.

By default, Windows restricts access to some event logs depending on the version of Windows you run. For example, only members of the local Administrators or global Domain Admins groups can read the Security event logs by default.

When you set up an Event Log monitoring input for WMI, the input connects to an AD domain controller to authenticate and, if necessary, perform any security ID (SID) translations before it begins to monitor the data.

The Event Log monitor uses the following logic to interact with AD after you set it up:

If you specify a domain controller when you define the input (with the evt_dc_name setting in inputs.conf), then the input uses that domain controller for AD operations.

If you do not specify a domain controller, then the input does the following:

The input attempts to use the local system cache to authenticate or resolve SIDs.

If the monitor cannot authenticate or resolve SIDs that way, it attempts a connection to the domain controller that the machine that runs the input used to log on.

If that does not work, then the input attempts to use the closest AD domain controller that has a copy of the Global Catalog.

If the domain controller that you specify is not valid, or a domain controller cannot be found, then the input generates an error message.

Collect event logs from a remote Windows machine

You have several choices to collect data from a remote Windows machine:

Use a universal forwarder

You can install a universal forwarder on the Windows machine and instruct it to collect event logs. You can do this manually, or use a deployment server to manage the forwarder configuration.

On the Windows machine that you want to collect Windows Event Logs, download the universal forwarder software from Splunk.

Run the universal forwarder installation package to begin the installation process.

When the installer prompts you, configure a receiving indexer.

When the installer prompts you to specify inputs, enable the event log inputs by checking the "Event logs" checkbox.

Complete the installation procedure.

On the receiving indexer, use Splunk Web to search for the event log data. An example search string follows:

host=<name of remote Windows machine> sourcetype=Wineventlog

Use WMI

If you choose to collect event logs remotely using WMI, you must install Splunk Enterprise to run as an Active Directory domain user. If the selected domain user is not a member of the Administrators or Domain Admins groups, then you must configure event log security to give the domain user access to the event logs.

To change event log security for access to the event logs from remote machines, you must:

Have administrator access to the machine from which you are collecting event logs.

Anomalous machine names are visible in event logs on some systems

On some Windows systems, you might see some event logs with randomly-generated machine names. This is the result of those systems logging events before the user has named the system, during the OS installation process.

This anomaly occurs only when you collect logs from the above-mentioned versions of Windows remotely over WMI.

Use Splunk Web to configure event log monitoring

To get local Windows event log data, point your Splunk instance at the Event Log service.

If you selected Forward, choose or create the group of forwarders you want this input to apply to. See "Forward data" in this manual.

Click Next.

Select the input source

In the left pane, select Local Event Logs

In the Select Event Logs list box, choose the Event Log channels you want this input to monitor.

Click once on each Event Log channel you want to monitor. Splunk Enterprise moves the channel from the "Available items" window to the "Selected items" window.

To unselect a channel, click on its name in the "Available Items" window. Splunk Enterprise moves the channel from the "Selected items" window to the "Available items" window.

To select or unselect all of the event logs, click on the "add all" or "remove all" links. Important: Selecting all of the channels can result in the indexing of a lot of data, possibly more than your license allows.

Click Next.

Specify input settings

The Input Settings page lets you specify application context, default host value, and index. All of these parameters are optional.

Host only sets the host field in the resulting events. It does not direct Splunk Enterprise to look on a specific machine on your network.

Select the appropriate Application context for this input.

Set the Host name value. You have several choices for this setting. Learn more about setting the host value in About hosts.

Set the Index that Splunk Enterprise should send data to. Leave the value as "default", unless you have defined multiple indexes to handle different types of events. In addition to indexes for user data, Splunk Enterprise has a number of utility indexes, which also appear in this dropdown box.

Click Review.

Review your choices

After you specify all your input settings, you can review your selections. Splunk Enterprise lists all options you selected, including the type of monitor, the source, the source type, the application context, and the index.

Review the settings.

If they do not match what you want, click < to go back to the previous step in the wizard. Otherwise, click Submit.

In the Event Log collection name field, enter a unique name for this input that you will remember.

In the Choose logs from this host field, enter the host name or IP address of the machine that contains the Event Log channels you want to monitor.

Click the Find logs button to refresh the page with a list of available Event Log channels on the machine you entered.

Click once on each Event Log channel you want to monitor. Splunk Enterprise moves the channel from the "Available items" window to the "Selected items" window.

To unselect a channel, click on its name in the "Available Items" window. Splunk Enterprise moves the channel from the "Selected items" window to the "Available items" window.

To select or unselect all of the event logs, click on the "add all" or "remove all" links.

In the Collect the same set of logs from additional hosts field, enter host names or IP addresses of additional machines that contain the Event Logs you selected previously. Separate multiple machines with commas.

You can always review the defaults for a configuration file by looking at the examples in %SPLUNK_HOME%\etc\system\default or at the spec file in the Admin Manual.

Event log monitor configuration values

Windows event log (*.evt) files are in binary format. You cannot monitor them like you do a normal text file. The splunkd service monitors these binary files by using the appropriate APIs to read and index the data within the files.

Splunk Enterprise uses the following stanzas in inputs.conf to monitor the default Windows event logs:

Monitor non-default Windows event logs

You can also configure Splunk Enterprise to monitor non-default Windows event logs. Before you can do this, you must import them to the Windows Event Viewer. After you import the logs, you can add them to your local copy of inputs.conf, as follows:

Disable an event log stanza

To disable indexing for an event log, add disabled = 1 below its listing in the stanza in %SPLUNK_HOME%\etc\system\local\inputs.conf.

Configuration settings for monitoring Windows Event Logs

Splunk software uses the following settings in inputs.conf to monitor Event Log files:

Attribute

Description

Default

start_from

How events are to be read. Acceptable values are oldest (meaning read logs from the oldest to the newest) and newest (meaning read logs from the newest to the oldest.)

You cannot set this attribute to newest while also setting the current_only attribute to 1.

oldest

current_only

How events are to be indexed. Acceptable values are 1 (where the input acquires events that arrive after the input starts for the first time, like 'tail -f' on *nix systems) or 0 (where the input gets all existing events in the log and then continues to monitor incoming events in real time.)

You cannot set this attribute to 1 and also set the start_from attribute to newest.

0

checkpointInterval

How frequently, in seconds, the Windows Event Log input saves a checkpoint.

Checkpoints store the eventID of acquired events to enable Splunk software to resume monitoring at the correct event after a shutdown or outage.

0

evt_resolve_ad_ds

The domain controller Splunk software uses to interact with Active Directory while indexing Windows Event Log channels. Valid only when you set the evt_resolve_ad_obj attribute to 1 and omit the evt_dc_name attribute.

Valid values are auto (meaning choose the nearest domain controller to bind to for AD object resolution) or PDC (meaning bind to the primary domain controller for the AD site that the host is in.) If you also set the evt_dc_name attribute, Splunk software ignores this attribute.

When you set this value to 1, you can optionally specify the Domain Controller name and/or DNS name of the domain to bind to, which Splunk software uses to resolve the AD objects. If you do not set this value, Splunk software attempts to resolve the AD objects.

0

evt_dc_name

Which Active Directory domain controller to bind to resolve AD objects. This name can be the NetBIOS name of the domain controller, the fully-qualified DNS name of the domain controller, or an environment variable name, specified as $Environment_variable.

If you set this attribute, then Splunk software ignores the evt_resolve_ad_ds attribute, which controls how the software determines the best domain controller to bind to for AD object resolution.

If you specify an environment variable, you must prepend a dollar sign ($) to the environment variable name. Splunk software uses the specified environment variable as the domain controller to connect to for AD object resolution. For example, to use the %LOGONSERVER% variable, specify evt_dc_name = $logonserver.

You can precede either format with two backslash characters. This attribute does not have a default.

N/A

evt_dns_name

The fully-qualified DNS name of the domain to bind to resolve AD objects.

N/A

suppress_text

Whether to include the message text that comes with a security event. A value of 1 suppresses the message text, and a value of 0 preserves the text.

0

use_old_eventlog_api

Whether or not to read Event Log events with the Event Logging API.

This is an advanced setting. Contact Splunk Support before you change it.

If set to true, the input uses the Event Logging API (instead of the Windows Event Log API) to read from the Event Log on Windows Server 2008, Windows Vista, and later installations.

false (Use the API that is specific to the OS.)

use_threads

Specifies the number of threads, in addition to the default writer thread, that can be created to filter events with the blacklist/whitelist regular expression.

This is an advanced setting. Contact Splunk Support before you change it.

The maximum number of threads is 15.

0

thread_wait_time_msec

The interval, in milliseconds, between attempts to re-read Event Log files when a read error occurs.

This is an advanced setting. Contact Splunk Support before you change it.

5000

suppress_checkpoint

Whether or not the Event Log strictly follows the 'checkpointInterval' setting when it saves a checkpoint.

This is an advanced setting. Contact Splunk Support before you change it.

By default, the Event Log input saves a checkpoint from between zero and checkpointInterval seconds, depending on incoming event volume.

false

suppress_sourcename

Whether or not to exclude the 'sourcename' field from events.

This is an advanced setting. Contact Splunk Support before you change it.

When set to true, the input excludes the 'sourcename' field from events and thruput performance (the number of events processed per second) improves.

false

suppress_keywords

Whether or not to exclude the 'keywords' field from events.

This is an advanced setting. Contact Splunk Support before you change it.

When set to true, the input excludes the 'keywords' field from events and thruput performance (the number of events processed per second) improves.

false

suppress_type

Whether or not to exclude the 'type' field from events.

This is an advanced setting. Contact Splunk Support before you change it.

When set to true, the input excludes the 'type' field from events and thruput performance (the number of events processed per second) improves.

false

suppress_task

Whether or not to exclude the 'task' field from events.

This is an advanced setting. Contact Splunk Support before you change it.

When set to true, the input excludes the 'task' field from events and thruput performance (the number of events processed per second) improves.

false

suppress_opcode

Whether or not to exclude the 'opcode' field from events.

This is an advanced setting. Contact Splunk Support before you change it.

When set to true, the input excludes the 'opcode' field from events and thruput performance (the number of events processed per second) improves.

false

whitelist

Whether to index events that match the specified text string. This attribute is optional.

You can specify one of two formats:

One or more Event Log event codes or event IDs (Event Code/ID format.)

One or more sets of keys and regular expressions (Advanced filtering format.)

You cannot mix formats in a single entry. You also cannot mix formats in the same stanza.

Splunk software processes whitelists first, then blacklists. If no whitelist is present, all events are indexed.

When you use the Event Code/ID format:

For multiple codes/IDs, separate the list with commas.

For ranges, use hyphens (for example "0-1000,5000-1000").

When using the advanced filtering format:

Use '=' between the key and the regular expression that represents your filter (for example "whitelist = EventCode=%^1([8-9])$%"

You can have multiple key/regular expression sets in a single advanced filtering entry. Splunk Enterprise conjuncts the sets logically. This means that the entry is valid only if all of the sets in the entry are true.

You can specify up to 10 whitelists per stanza by adding a number to the end of the whitelist attribute, for example whitelist1...whitelist9.

N/A

blacklist

Do not index events that match the text string specified. This attribute is optional.

One or more sets of keys and regular expressions. (Advanced filtering format.)

You cannot mix formats in a single entry. You also cannot mix formats in the same stanza.

Whitelists are processed first, then blacklists. If no blacklist is present, all events are indexed.

When using the Event Log code/ID format:

For multiple codes/IDs, separate the list with commas.

For ranges, use hyphens (for example "0-1000,5000-1000").

When using the advanced filtering format:

Use '=' between the key and the regular expression that represents your filter (for example "blacklist = EventCode=%^1([8-9])$%"

You can have multiple key/regular expression sets in a single advanced filtering entry. Splunk software conjuncts the sets logically. This means that the entry is valid only if all of the sets in the entry are true.

You can specify up to 10 blacklists per stanza by adding a number to the end of the blacklist attribute, for example blacklist1...blacklist9.

renderXml

Render event data as XML supplied by the Windows Event Log subsystem. This setting is optional.

A value of '1' or 'true' means to render the events as XML. A value of '0' or 'false' means to render the events as plain text.

If you set renderXml to true, if you want to also create whitelists or blacklists to filter event data, you must use the $XmlRegex special key in your whitelists or blacklists.

0 (false)

index

The index that this input should send the data to.

the default index

disabled

Whether or not the input should run.

Valid values are 0 (meaning that the input should run) and 1 (meaning that the input should not run.

0

Use the Security event log to monitor changes to files

You can monitor changes to files on your system by enabling security auditing on a set of files and/or directories and then monitoring the Security event log channel for change events. The event log monitoring input includes three attributes which you can use in inputs.conf. For example:

You can also use the suppress_text attribute to include or exclude the message text that comes with a security event.

When you set suppress_text to 1 in a Windows Event Log Security stanza, the entire message text does not get indexed. This includes any contextual information about the security event. If you need this contextual information, do not set suppress_text in the stanza.

Create advanced filters with 'whitelist' and 'blacklist'

You can perform advanced filtering of incoming events with the whitelist and blacklist settings in addition to filtering based solely on event codes. To do this, specify the key/regular expression format in the setting:

whitelist = key=<regular expression> [key=<regular expression>] ...

In this format, key is a valid entry from the following list:

Key

Description

$TimeGenerated

The time that the computer generated the event. Splunk Enterprise only generates the time string as the event.

$Timestamp

The time that the event was received and recorded by the Event Log service. Splunk Enterprise only generates the time string as the event.

$XmlRegex

A special key that tells Splunk Enterprise to filter on events generated in XML. To use this key, set it to the value that you want Splunk Enterprise to filter on. You must configure the input that you want to blacklist or whitelist to render events in XML by using the renderXml = true setting under that input stanza. Splunk Enterprise conjuncts multiple entries in a single whitelist or blacklist line; all of the entries must match for the filter to trigger.

Category

The category number for a specific event source.

CategoryString

A string translation of the category. The translation depends on the event source.

ComputerName

The name of the computer that generated the event.

EventCode

The event ID number for an event. Corresponds to "Event ID" in Event Viewer.

An element used to classify different types of events within an event log channel. The Security Event Log channel has this element, for example.

LogName

The name of the Event Log channel that received the event. Corresponds to "Log Name" in Event Viewer.

Message

The text of the message in the event.

OpCode

The severity level of the event ("OpCode" in Event Viewer.)

RecordNumber

The Windows Event Log record number. Each event on a Windows machine gets a record number. This number starts at 0 with the first event generated on the system, and increases with each new event generated, until it reached a maximum of 4294967295. It then rolls back over to 0.

The user associated with the event. Correlates to "User" in Event Viewer.

and <regular expression> is any valid regular expression that represents the filters that you want to include (when used with the whitelist attribute) or exclude (when used with the blacklist attribute).

You can specify more than one key/regular expression set on a single entry line. When you do this, Splunk Enterprise logically conjuncts the sets. This means that only events that satisfy all of the sets on the line are valid for inclusion or exclusion. For example, this entry:

whitelist = EventCode="^1([0-5])$" Message="^Error"

means to include events that have an EventCode ranging from 10 to 15 and contain a Message that begins with the word Error.

You can specify up to 10 separate whitelist or blacklist entries in each stanza. To do so, add a number at the end of the whitelist or blacklist entry on a separate line:

You cannot specify an entry that has more than one key/regular expression set that references the same key. If, for example, you specify:

whitelist = EventCode="^1([0-5])$" EventCode="^2([0-5])$"

Splunk Enterprise ignores the first set and only attempts to include events that match the second set. In this case, only events that contain an EventCode between 20 and 25 match. Events that contain an EventCode between 10 and 15 do not match. Only the last set in the entry ever matches. To resolve this problem, specify two separate entries in the stanza:

Resolve Active Directory objects in event log files

To specify whether Active Directory objects like globally unique identifiers (GUIDs) and security identifiers (SIDs) are resolved for a given Windows event log channel, use the evt_resolve_ad_obj attribute (1=enabled, 0=disabled) for that channel's stanza in your local copy of inputs.conf. The evt_resolve_ad_obj attribute is on by default for the Security channel.

To specify a domain controller for the domain that Splunk should bind to in order to resolve AD objects, use the evt_dc_name attribute.

The string specified in the evt_dc_name attribute can represent either the domain controller NetBIOS name, or its fully-qualified domain name (FQDN). Either name type can, optionally, be preceded by two backslash characters.

The following examples are correctly formatted domain controller names:

FTW-DC-01

\\FTW-DC-01

FTW-DC-01.splunk.com

\\FTW-DC-01.splunk.com

To specify the FQDN of the domain to bind to, use the evt_dns_name attribute.

Constraints for using the evt_dc_name and evt_resolve_ad_obj attributes

When you use the evt_resolve_ad_obj and evt_dc_name attributes:

Splunk software first attempts to resolve SIDs and GUIDs using the domain controller (DC) specified in the evt_dc_name attribute first. If it cannot resolve SIDs using this DC, it attempts to bind to the default DC to perform the translation.

If Splunk software cannot contact a DC to translate SIDs, it attempts to use the local machine for translation.

If none of these methods works, then Splunk prints the SID as it was captured in the event.

Splunk software cannot translate SIDs that are not in the format S-1-N-NN-NNNNNNNNNN-NNNNNNNNNN-NNNNNNNNNN-NNNN.

If you discover that SIDs are not being translated properly, review %SPLUNK_HOME%\var\log\splunkd.log for clues on what the problem might be.

Specify whether to start index at the earliest or the most recent event

Use the start_from attribute to specify whether events are indexed starting at the earliest event or the most recent. By default, indexing starts with the oldest data and moves forward. Do not change this setting, because Splunk software stops indexing after it has indexed the backlog using this method.

Use the current_only attribute to specify whether to index all preexisting events in a given log channel. When set to 1, only events that appear from the moment the Splunk deployment was started are indexed. When set to 0, all events are indexed.

When you instruct Splunk Enterprise to render events in XML, event keys within the XML event render in English regardless of the machine system locale. Compare the following events generated on a French version of Windows Server:

The Data Name keys in the XML event render in English despite rendering in the system's native language in the standard event.

Use blacklists and whitelists to filter on XML-based events

If you render events in XML, and you want to use whitelists and blacklists to filter on those events, you must use the special key $XmlRegex when you build your whitelists or blacklists. The whitelist or blacklist triggers when the value that you specify with $XmlRegex is found anywhere in the rendered XML event. $XmlRegex does not function if you do not explicitly specify the input to render in XML with the renderXml = true setting.

Following is an example of using whitelists on XML events. Splunk Enterprise indexes all XML events that contain the word "Error":

Index exported event log (.evt or .evtx) files

Do not attempt to monitor an .evt or .evtx file that is open for writing. Windows does not allow read access to these files. Use the event log monitoring feature instead.

Constraints for monitoring Windows Event log files directly

As a result of API and log channel processing constraints on Windows XP and Server 2003 systems, imported .evt files from those systems do not contain the "Message" field. This means that the contents of the "Message" field do not appear in your Splunk index.

Splunk Enterprise on Windows Vista and later and Server 2008/2008 R2 and later can index both .evt and .evtx files.

If your .evt or .evtx file is not from a standard event log channel, you must make sure that any dynamic link library (DLL) files required by that channel are present on the computer on which you are indexing.

Splunk Enterprise indexes an .evt or .evtx file in the primary locale/language of the computer that collects the file.

Files that have been exported from another machine do not work with the Splunk Web Upload feature. This is because those files contain information that is specific to the machine that generated them. Other machines won't be able to process the files in their unaltered form.

When producing .evt or .evtx files on one system, and monitoring them on another, it's possible that not all of the fields in each event expand as they would on the system producing the events. This is caused by variations in DLL versions, availability and APIs. Differences in OS version, language, Service Pack level and installed third party DLLs, etc. can also have this effect.

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